Pump



` Nov. 1927.

1,649,347 A. HARDT PUMP Filed July 13, 1926 In'vzzol' f r/wr Hardt Patentedl Nov. 15, ,1927i l "1,649,341 -UNITI-:o STATES Y Param( oFFlcE.

ARTHUR'HABDT, or' GoDEsBERG, annulant?.

Application llled July 13, 1926, Serial No, 122,120, and' in Germany July 23, 192,5.

J With pumps used in connection with hydraulic gearings for mot-or cars, lifting deq vices, hydraulic presses, and the like, the depressure with the motor driving the pump it;

liverypressure increases with the increase of' the resistance.

In order to be in theV posi' tion to overcome that increasing delivery has Abecome customary to decrease the amount to be delivered in proportion to the increase of the delivery pressure,- for 1nstance by varying the. eccentricity of an Aeccentric disk or ring or of a crank or the like -so as to accommodate the stroke -of the the other condition.

- As adjusting manuallythe amount to ,be

l delivered requires at least .in certain'cases, *for instancefwhere hydraulic gearlngs are employed in connection with 4motor cars,l

pretty great-'attention on the side of the operator, maybe of the driverl ofthe motorcar, it has been endeavored to provide for effecting that adjustment automatically, and it has for this purpose been proposed to make use. of an intermittently and automatically acting intermediate member, for instance a piston, so arranged as to be ada ted to adjust automatically the amount del1vered and to be acted on one side Byethe delivery pressure vand on the other side by an elastic medium.

Ifcompressed air orcompr'essed gas is used as the elastic medium and if the air or gas cushion is sosdevised that its pressure is always varied approximately proportionally to the length of the pathcovered by said means independent of its' preliminary ten sion,- then the advantage is attained that the product of delivery pressureand amount delivered remains approximately constant' atany delivery pressure, -so that also the driving -motor is, loaded approximately constant at all delivery pressures.

ion at a constanthigh Therefore according.

to the invention the-air or gas cushion is connected 1. e.'by means of a non-return-stroke valve with a compressed gas or air source maintaining the initial pressure of the gas Vor air. The invention is .illustrated diagrammaticallyand by way of-example on the accom panylng Vdrawing on which aconstructional 4'of rotation 'of the rotor a.

'farm of a device designed according to the invention is shown in longitudinal section.

Theinvention is illustrated diagrammatically and by way of example on the accompanying drawing showing a verticall longitudinal section lthrough a device designed ac"- cording to this invention.

Referring to the drawing, a denotes the rotor of a rotaryy pump having six pistons 1, 2, 3,4,.5, 6 which rotate together with said rotor and are at the same time reciprocated in the same by the co-operation of. rolls :v attachedto the outer ends of the pis-| tons, and of the inne-rcircumferential surface of the annular stator b. a denotes the vstationary slide-valvewhich is located centrally said rotor a. This latter Aand the stator or ring b arefarranged eccentrically with respect to VYeach other, as shown. The leccentricity can be varied (by means hereinafter described) by shifting the stator or ring b, more or less from the right to the isting below the pistons just located in the upper half of the rotor, the filled cylinders half ofA their path. The liquid is pressed first into the chamber below the slide-valve and then into the delivery pipe e.

In the position of the rotor or rotary body a andthe ring b relatively to each other as shown in the drawing the quantity delivered being emptied by their appertaining pisv tons `when these move through the lower by the six pistons and cylinders, or the six y pumps respectively, is the largest because the eccentriclty Vof the ring Z2. relatively to the body a is vthe greatest possible. If the ring b is shifted to the left` the quantity of liquid b is shifted so much t at its vcentre and that delivered will be depased, and if tliering of the body a coinci e, the quantity will be diminished to zero. The pressure which the driving motor can overcome with an equal 'turning moment increases 1n the same ratio.

The automatic accommodation of the de-A livery pressure to the pressure resistance s eifected by the means of a 'piston -f rigidly connected with the ring b and being shift' able in the cylinder g into which oil can be i conducted from the pipe e by means of a branch pipe e1. The piston f is connected rigidly with a larger piston h which is shiftable 1n a cylinder i and subjected to the pressure of compressed air.

`Supposing, the ratio between the compressed air present in the cylinder i and the liquid pressure the driving motor vcan produce at the largest amount 4of liquid delivered, as well as at the most favorable ettieiency, be inverse to the ratio between the sectional area of the p-iston f and that of vthe p-iston h, then in the same moment in which the pressure in the pipe e rises even only quite a little the piston f will be shifted to the left for a corresponding length of way and, consequently,l also the piston h will be shifted whereby the pressure of the air present in thecylinder z' is also corre` spondingly increased, lthe leftward movement continuin until the proportionality mentioned' in t e preceding lines of this paragraph, viz, (between the pressure of the liqlliid and that of the air, has been re-establis ed. Together with the pistons hand f also the ring b will be shifted to the left, in consequence whereof, firstly, the quantity Ofliquid delivered by the pumps 1-6 is diminished correspondingly, and secondly, the pressure which the driving motorcan overcome at the same turning moment is increased correspondingly.

If the axial length of the cylinder i or, `more precisely, of the path of the piston h, corresponds' to the greatesteccentricity existing between the ring b and the rotatoryl body a, then the delivery pressure which the driving motor can overcome at the same turning moment will, theoretically (as the compression of'the air takes place nearly isothermically owing to the large cooling surfaces), be accommodated accurately to the variation of the delivery resistance.

If the normal delivery pressure amounts, for instance, to 10 atm., the length ofthe path of the piston to 2O cm. and the length of the air cushion to 10 om., and if, furthermore, the delivery pressure rises,`owing to an increase of the resistance, to20 atm., then also the pressure exerted by the liquid piston upon the air cushion enclosed in the chamber will be doubled, in consequence where ofthe volume of the air will be reduced to one half according to Gay-Lussacs law, the piston' h will be shifted-to the left by .5 om., and the stroke of the piston reduced to one half, so that the product of delim pressure and amount of liquid delivered remain unchanged.

If the pressure should rise to 30 atm., then also the ressure to which the air-cushion i is subjec will become the threefold of what it had been initially, and the 'air will be compressed to one third of its initial vol- Aurne;

as a further consequence the stroke of the pump piston will be reduced to one third of its initial length', so that the product of delivery pressure and amount delivered rering b from the shortest to the longest stroke of the piston in order to make upl for the decrease of the etiiciency arising when the amount delivered is only small.

If for any reason,.for instance, in consequence of the unavoidable leakinessof the piston, a pressure loss is caused in the chamber z', the motor will not be economically loaded. To obviate this draw-back according to the invention the chamber i is-connected by a return-stroke valve m with a l compressed gas or air source, for instance a reservoir n maintaining the initial pressure of the gas or air cushion bytilling up the Veventual gas losses in the chamber i at those times at which only the normal fluid pressure is operative lagainst the air cushion.

The preliminary tension of the air cushion z' is preferably made adjustable, for instance, by irst regulating the pressure in the chamber n, and then adjusting corre'- spondingly the pressure in the chamber 'i by opening the non-return valve m in the Vessel n. This latter may be provided for that purpose'with a branchprovidedwith a cock y or any other suitable device permitting either to blow off the pressure more or less or to increase it by means of a pump or fa liquid unde'r pressure. Reducing the pressure may become necessary, for instance, if a cylinder or several cylinders of an internal combustion" engine driving the pump fail from an reason, for instance by having been damage and the service is to be continued with the remaining cylinder or cylinders which cannot, of course, produce the normal .pressure Y and deliver the same amount of liquid than prior to the'changed state.

I n the constructional form shown by way of example a second hydraulic piston o connected rigidly with the other pistons and located in a cylinder p is provided this cylinder is connected by a branch pipe e with the pipe e1, and a three-way cock 1' is 1nserted into this-connection. If the position of the plug of the cock is that shown inthe drawing so that the liquid under pressure. can iow from the pipe e1 not only into the cylinder g, but into the c linder p, also, the pressures exertedfu-pon t e pistons f and o act together, but if the position ofthe plug j is such that the liquid leaves the cock through -the lateral aperture rl-of the Vcock casingthat additional pressure (on the piston o) does not exist. The object ofthis additional device is to place the attendant or the driver into the position to avail himself suddenly of an `excess ofpower as rei quired, for instance, at starting a motor-car.

" I claim: A

' 1. -A pump for' hydraulic gearings', lifting devices, hydraulic presses, and the like, comprising, in combina-tion with the respective pump proper, means adapted to'regulate the quantity of liquid under pressure delivered 'by the pump, an adjustable member connected with said first'means for the purpose of adjusting it and being actuated in one direction by 'the pressure produced by the pump. a gas cushion actua-ting said adjustable member in the opposite direction, having a certain preliminary tension and being adapted to vary its pressure ,proportional to the lengthof the path covered by said adjustable member and means adapted to automatically maintain the said preliminary tension. i f

2. A pump for hydraulic gearings, lifting devices, hydraulic presses` and the like, comprising, in combination 'with the respective. pump proper, means adapted to regulate the quantity of liquid under "pressure delivered by the pump, an. adjustable member connected With said'frst means for-the purpose 'of adjusting it and,being actuated in one i Ameans adapted to automaticallylmaintan the y 35 said preliminary tension.

direction by the pressure produced by the pump, a as cushion actuating said adjustable mem rin theopposite direction, hav-l ing a preliminary'tension exertingon said adjustable member a pressure corresponding to the pressure eerted in the opposite direc' .tion by. the normal delivery pressure. and

pump for hydraulic geaiin lifting devices, hydraulic presses, and the isllxe, comprising, in combination wpitli the respective pump proper, means adapted to regulate-fthe quantity of-liquid under pressure delivered by the pump, an 'adjustable member connected with said first means for the *purpose of adjusting it and being actuated in one direction by the pressure produced bY the pump, agas cushion actuating said a ustable member in the opposite'direct-ion, avL

ving a certain preliminary tension and being adapted' to vary its pressure proportional to bythe pump, an adjustable member oon- ;'r nected with said rst means for thepurpose of adjusting it and beingactuated in one direction by the pressure'produoedbyf pump, a gas cushion actuating said a able member in the opposite direction', `a,ving a preliminary vtension exerting on said the adjustable member a pressure corresponding 1 to the pressure Aexerted in the opposite direc-` tion by the normal delivery pressure, means adapted to automatically Vmaintain the said preliminary tension and means for adjusting said preliminary tension. a Y Y In testimony whereof I have nixed my signature. a ,Y 

